The growth of a normal cell or of a virus in its host cell involves a complex pattern of gene expression in which individual genes or groups of genes are activated or repressed at appropriate time during growth. Studies of the growth of bacterial cells and of bacteriophanges have provided an important model system for the study of how gene expressin is regulated. Those studies suggest that regulation of transcription - DNA dependent synthesis of messenger RNA - is of major importance in the control of gene expression. We propose to continue our study of the steps involved in enzymatic transcription. We will focus primarily on the transcription of bacteriophange T7 DNA and on the manner in which enzymatic transcription is activated and repressed during T7 phnge growth. The T7 RNA polymerase will be studied and example of a viral specific transcriving enzyme. Specific goals will be: (1) The continuation of studies on the steps involved in selective RNA chain initiation and termination by bacterial RNA polymerase and of the T7 mRNA synthesized in vitro by this enzyme, (2) Physical and biochemical studies on the T7 induced RNA polymerase including studies of the protein, on the steps involved in enzymatic RNA synthesis and on the T7 mRNA synthesized by this enzyme, (3) completion of a transcription map for the late region of T7 DNA (4) studies on the nature of the genetic information in T7 promoter sites.